Paper/patches/server/0569-MC-4-Fix-item-position-desync.patch

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2021-06-14 20:50:22 +02:00
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: BillyGalbreath <blake.galbreath@gmail.com>
Date: Tue, 8 Dec 2020 20:24:52 -0600
Subject: [PATCH] MC-4: Fix item position desync
This fixes item position desync (MC-4) by running the item coordinates
through the encode/decode methods of the packet that causes the precision
loss, which forces the server to lose the same precision as the client
keeping them in sync.
diff --git a/src/main/java/com/destroystokyo/paper/PaperConfig.java b/src/main/java/com/destroystokyo/paper/PaperConfig.java
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index 652d87fc5d566dba8018c81676329f0e0bca471b..c56e7fb18f9a56c8025eb70a524f028b5942da37 100644
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--- a/src/main/java/com/destroystokyo/paper/PaperConfig.java
+++ b/src/main/java/com/destroystokyo/paper/PaperConfig.java
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@@ -474,4 +474,9 @@ public class PaperConfig {
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private static void trackPluginScoreboards() {
trackPluginScoreboards = getBoolean("settings.track-plugin-scoreboards", false);
}
+
+ public static boolean fixEntityPositionDesync = true;
+ private static void fixEntityPositionDesync() {
+ fixEntityPositionDesync = getBoolean("settings.fix-entity-position-desync", fixEntityPositionDesync);
+ }
}
diff --git a/src/main/java/net/minecraft/network/protocol/game/ClientboundMoveEntityPacket.java b/src/main/java/net/minecraft/network/protocol/game/ClientboundMoveEntityPacket.java
index b30c08bfb8c55161543a4ef09f2e462e0a1fe4ae..ec93f5300cc7d423ec0d292f0f8443f900d72dab 100644
--- a/src/main/java/net/minecraft/network/protocol/game/ClientboundMoveEntityPacket.java
+++ b/src/main/java/net/minecraft/network/protocol/game/ClientboundMoveEntityPacket.java
@@ -21,11 +21,11 @@ public abstract class ClientboundMoveEntityPacket implements Packet<ClientGamePa
protected final boolean hasPos;
public static long entityToPacket(double coord) {
- return Mth.lfloor(coord * 4096.0D);
+ return Mth.lfloor(coord * 4096.0D); // Paper - check ItemEntity#setPosRaw on update
}
public static double packetToEntity(long coord) {
- return (double)coord / 4096.0D;
+ return (double)coord / 4096.0D; // Paper - check ItemEntity#setPosRaw on update
}
public Vec3 updateEntityPosition(Vec3 orig) {
diff --git a/src/main/java/net/minecraft/world/entity/Entity.java b/src/main/java/net/minecraft/world/entity/Entity.java
index 9c37264884d1353de9b1ef388773d1991f5db2b4..bf8e02e23fce3c48fc07c0bdb4ac137c8ba13e03 100644
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--- a/src/main/java/net/minecraft/world/entity/Entity.java
+++ b/src/main/java/net/minecraft/world/entity/Entity.java
@@ -3754,6 +3754,16 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, n
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}
public final void setPosRaw(double x, double y, double z) {
+ // Paper start - fix MC-4
+ if (this instanceof ItemEntity) {
+ if (com.destroystokyo.paper.PaperConfig.fixEntityPositionDesync) {
+ // encode/decode from PacketPlayOutEntity
+ x = Mth.lfloor(x * 4096.0D) * (1 / 4096.0D);
+ y = Mth.lfloor(y * 4096.0D) * (1 / 4096.0D);
+ z = Mth.lfloor(z * 4096.0D) * (1 / 4096.0D);
+ }
+ }
+ // Paper end - fix MC-4
// Paper start - never allow AABB to become desynced from position
// hanging has its own special logic
if (!(this instanceof net.minecraft.world.entity.decoration.HangingEntity) && (this.position.x != x || this.position.y != y || this.position.z != z)) {